Polishing endpoint detecting method, device for detecting a polishing endpoint of a polishing process and chemical-mechanical polishing apparatus comprising the same

ABSTRACT

A polishing endpoint detecting device of a polishing apparatus detects a polishing endpoint of a polishing process by measuring light reflected from a surface of a semiconductor substrate being polished. The apparatus also includes a polishing pad and a rotary plate each of a light-transmitting material. The light is directed onto the surface of the semiconductor substrate through the polishing pad and the rotary plate and is scanned across the surface of the semiconductor substrate along a horizontal line which passes through the centers of the polishing pad and the semiconductor substrate. A light-measuring instrument measures a characteristic of the light reflected from the surface of the semiconductor substrate, and a processor detects the polishing endpoint by analyzing signals produced by the light measuring instrument.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a chemical-mechanical polishingprocess in which a film formed on a semiconductor substrate isplanarized. More particularly, the present invention relates to a deviceusing light for detecting an endpoint of the chemical-mechanicalpolishing process.

[0003] 2. Description of the Related Art

[0004] Recently, in an effort to meet consumer demand, advances intechnology for manufacturing semiconductor devices have been developedto enhance the integration density, reliability, and response speed,etc., of the devices. Generally, a semiconductor device is manufacturedby forming a film on a semiconductor substrate, such as a silicon wafer,and patterning the film to form a pattern having a required electricproperty.

[0005] The pattern is formed by means of sequential or repeated unitprocesses including deposition, photolithography, etching, ionimplantation, polishing, cleaning, and drying processes. Among theseunit processes, polishing is key in attaining a high degree ofintegration, and structural and electrical reliability of thesemiconductor device. In the chemical-mechanical polishing process, afilm on a semiconductor substrate is mainly planarized by a chemicalreaction between a slurry and the film formed on the semiconductorsubstrate and by mechanical friction between the film on thesemiconductor substrate and a polishing pad of a chemical-mechanicalpolishing (CMP) apparatus.

[0006] In addition to the polishing pad, the CMP apparatus generallyincludes a rotating table atop which the polishing pad is attached, apolishing head for holding and rotating a semiconductor substrate, aslurry supplying device for supplying slurry between the polishing padand the semiconductor substrate, and a pad conditioner for improving thesurface condition of the polishing pad. The CMP apparatus furtherincludes a polishing endpoint detecting device for determining theendpoint of the chemical-mechanical polishing process, i.e., the pointat which the polishing process should be stopped.

[0007] The conventional polishing endpoint detecting device measuresvariables related to the surface condition of the semiconductorsubstrate, and detects the polishing endpoint when the variables changeabruptly. For example, in the case in which an insulation film or adielectric film on semiconductor substrate is polished in order toexpose a metal layer formed beneath the insulation film or thedielectric film, the temperature of the semiconductor substrate, thecoefficient of friction, or a characteristic of light reflected from thepolished surface of the semiconductor substrate changes abruptly oncethe metal layer is exposed. The polishing endpoint detecting device isthus used to determine the polishing endpoint by detecting an abruptchange in these variables.

[0008] Polishing endpoint detecting devices are disclosed in U.S. Pat.No. 5,893,796 (issued to Birang et al.), U.S. Pat. No. 6,045,439 (issuedto Birang et al.), and U.S. Pat. No. 6,280,290 (issued to Birang etal.). These polishing endpoint detecting devices include a platen havinga hole, a polishing pad having a transparent window, and a laserinterferometer for detecting the polishing endpoint. Also, a method forforming the transparent window is disclosed. Furthermore, U.S. Pat. No.6,247,998 (issued to Wiswesser, et al.) discloses a CMP apparatus havinga platen for supporting a polishing pad, a polishing head for holding asemiconductor substrate, a first optical system for directing a firstlight onto a surface of a semiconductor substrate and for measuring thelight reflected from the semiconductor substrate in order to generate afirst interference signal, and a second optical system for directing asecond light onto the surface of the semiconductor substrate and formeasuring the light reflected from the substrate in order to generate asecond interference signal.

[0009]FIGS. 1 and 2 illustrate a conventional CMP apparatus 100 having apolishing endpoint detecting device. Referring FIG. 1, the conventionalCMP apparatus 100 includes a rotational table 110 to which a polishingpad 102 is attached, a polishing head 120, a pad conditioner 122 forimproving the surface condition of the polishing pad 102, and a slurrysupplying member 124 for supplying a slurry 124 a between asemiconductor substrate 10 and the polishing pad 102. The polishing head120 holds the semiconductor substrate 10 so that a surface 10 a of thesemiconductor substrate 10 to be polished faces the polishing pad 102.In addition, the polishing head 120 places the surface 10 a of thesemiconductor substrate 10 to be polished in contact with the polishingpad 102.

[0010] The rotational table 110 has a rotary plate 112 to which thepolishing pad 102 is attached, a base plate 116 coupled to a rotaryshaft 126, and a sidewall 114 disposed between the rotary plate 112 andthe base plate 116. The rotational table 110 thus has the overall shapeof a disc, wherein the sidewall 114 extends along the outer peripheraledges of the rotary plate 112 and the base plate 1 1-6.

[0011] A polishing endpoint detecting device 130 for detecting thepolishing endpoint of the chemical-mechanical polishing process isinstalled in a space defined by the rotary plate 112, the side wall 114and the base plate 116. The polishing endpoint detecting device 130includes a light source 134 for generating a beam of light 132 a, asplitter 136 for directing the light 132 a generated by the light source134 onto the surface 10 a of the semiconductor substrate 10 beingpolished, a light measuring instrument 138 for measuring acharacteristic of the light 132 c reflected from the surface 10 a of thesemiconductor substrate 10, and a processor 140 for detecting thepolishing endpoint by analyzing the signals produced by the lightmeasuring instrument 138.

[0012] Furthermore, the rotary plate 112 has a hole 112 a therethrough,and the polishing pad 102 has a transparent window 104 at a locationcorresponding to the hole 112 a. The light 132 b is directed by thesplitter 136 onto the surface 10 a of the semiconductor substrate 10being polished through the hole 112 a and the transparent window 104.The light 132 c reflected from the semiconductor substrate 10 passesback through the window 104 and hole 112 a to the light measuringinstrument 138. The light measuring instrument 138 measures theinterference of the light 132 c reflected from the semiconductorsubstrate 10 or the flux of the reflected light 132 c that is dependenton a reflection ratio of the semiconductor substrate 10.

[0013] However, a gap exists between the surface 10 a of thesemiconductor substrate 10 and the transparent window 104 of thepolishing pad 102. The slurry 124 a supplied onto the polishing pad 102and a by-product of the polishing process accumulate in this gap betweenthe surface 10 a of the semiconductor substrate 10 and the transparentwindow 104. The accumulated slurry 124 a and by-product disperse thelight directed onto the face 10 a of the semiconductor substrate 10being polished. The amount of this dispersed light is proportional tothe amounts of the slurry 124 a and the by-product that have accumulatedbetween the surface 10 a of the semiconductor substrate 10 and thetransparent window 104. The dispersed light affects the reading given bythe light measuring instrument 138, whereby the polishing endpoint cannot be properly determined.

[0014] Referring now to FIGS. 1 and 2, the light 132 b applied to thesurface 10 a of the semiconductor substrate 10 is focused on apredetermined portion 10 b of the semiconductor substrate 10. However,different portions of the semiconductor substrate 10 may be polished atdifferent rates. Thus, when the polishing endpoint is established usingmeasurements taken at only a portion 10 b of the semiconductor substrate10, other portions of the semiconductor substrate 10 may be over- orunder-polished.

[0015] Meanwhile, the polishing pad 102 is attached to the rotary plate112 using an adhesive. When the polishing pad 102 is replaced, thepolishing pad 102 must be attached to the plate 112 so that thetransparent window 104 of the polishing pad 102 is aligned exactly withthe hole 112 a in the rotary plate 112. This alignment process requiresa significant amount of time even when the polishing pad is replaced bya highly skilled technician. Accordingly, replacing the polishing pad102 in a conventional CMP apparatus detracts significantly from theefficiency at which the chemical-mechanical polishing process can becarried out.

SUMMARY OF THE INVENTION

[0016] Objects of the present invention are to overcome above-mentionedproblems of the prior art.

[0017] Thus, for instance, a first object of the present invention is toprovide a polishing endpoint detecting device and a method of detectinga polishing endpoint which can be used to measure the amount by whichthe entire surface of a semiconductor substrate is polished.

[0018] Another object of the present invention is to provide a CMPapparatus having a polishing endpoint detecting apparatus which analyzeslight reflected from the semiconductor substrate to detect a polishingendpoint, and in which the polishing pad thereof can be changed in ashort amount of time.

[0019] According to one aspect of the present invention, a polishingendpoint detecting device comprises a light source for producing a beamof light, a light path changing means for scanning the lighthorizontally across the surface of the semiconductor substrate, and alight measuring instrument that measures a characteristic of the lightreflected from the surface of the substrate. A processor detects apolishing endpoint by analyzing signals produced by the light measuringinstrument.

[0020] According to another aspect of the present invention, a CMPapparatus comprises a rotational table including a rotary plateconsisting of a light-transmitting material, a polishing pad attached tothe rotary plate and also consisting of a light-transmitting material, apolishing head for holding a semiconductor substrate such that a surfaceof the semiconductor substrate to be polished faces the polishing padand is pressed into contact with the polishing pad, and a polishingendpoint detecting device. The polishing endpoint detecting deviceincludes a light source for producing a beam of light, a light measuringinstrument for producing signals indicative of a characteristic of thelight reflected from the surface, and a processor for detecting apolishing endpoint of the semiconductor substrate by analyzing thesignals produced by the light measuring instrument. Also, as per above,the polishing endpoint detecting device preferably also includes a lightpath changing means for scanning the light horizontally across thesurface of the semiconductor substrate along a line that passes throughthe center of rotation of the polishing pad.

[0021] The rotational table may also include a base plate disposed belowthe rotary plate and having a shape corresponding to that the rotaryplate, a sidewall extending along and between the outer peripheral edgesof the base plate and the rotary plate, and a rotary shaft connected tothe base plate. In this case, the light source, the light measuringinstrument and the light path changing means are disposed within therotational table as supported by the base plate. The processor isconnected to the light measuring instrument through the rotary shaft.

[0022] The light path changing means may comprise a reflective splitter,i.e., a mirror, for directing the light onto the surface of thesubstrate, and a driving means for rotating the splitter so that thelight scans the surface. Alternatively, the light path changing meansmay comprise a supporting member that supports the light source and thelight measuring instrument, and driving means for moving the supportingmember reciprocally along a straight direction so that the light fromthe light source scans the surface of the substrate.

[0023] According to an aspect the present invention as described above,during the polishing process while the surface of the substrate is beingpressed against the polishing pad and the polishing pad is being rotatedrelative to the surface of the substrate, the light path changing meanschanges scans the light emanating from the light source along ahorizontal line across the surface of the semiconductor substrate.Preferably, this horizontal line passes through a center of rotation ofthe rotary plate and polishing pad and/or through the center of thesurface of the substrate being polished. The light measuring instrumentproduces signals representative of a characteristic of the lightreflecting from the surface of the substrate, and the processor detectsa polishing endpoint by analyzing the signals produced from the lightmeasuring instrument. Because the amount(s) by which the entire surfaceof the substrate is polished can be measured in this way, thesemiconductor substrate can be prevented from being over-polished orunder-polished.

[0024] In addition, the present invention does away with the need for atransparent window in the polishing pad because the rotary plate andpolishing pad are made of light-transmitting materials. Therefore, thepolishing pad can be changed in a relatively short amount of time.Furthermore, the polishing endpoint is detected with a high degree ofreliability because little of the slurry or by-product of the polishingprocess accumulates between the polishing pad and the semiconductorsubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other objects, features and advantages of thepresent invention will become more apparent from the following detaileddescription of the preferred embodiments thereof made with reference tothe accompanying drawings, of which:

[0026]FIG. 1 is a schematic cross-sectional view of a conventional CMPapparatus;

[0027]FIG. 2 is an enlarged plan view of the CMP apparatus shown in FIG.1;

[0028]FIG. 3 is a schematic cross-sectional view of a CMP apparatushaving a first embodiment of a polishing endpoint detecting deviceaccording to the present invention;

[0029]FIG. 4 is an enlarged plan view of the CMP apparatus shown in FIG.3;

[0030]FIG. 5 is a detailed cross-sectional view of the splitter of thepolishing endpoint detecting device of the apparatus shown in FIG. 3;

[0031]FIG. 6 is a side view of the splitter and the light measuringinstrument of the polishing endpoint detecting device of the apparatusshown in FIG. 3;

[0032]FIG. 7 is a schematic cross-sectional view of a CMP apparatushaving a second embodiment of a polishing endpoint detecting deviceaccording to the present invention;

[0033]FIG. 8 is a schematic cross-sectional view of a CMP apparatushaving a third embodiment of a polishing endpoint detecting deviceaccording to the present invention;

[0034]FIG. 9 is a schematic cross-sectional view of a CMP apparatushaving a fourth embodiment of a polishing endpoint detecting deviceaccording to the present invention;

[0035]FIG. 10 is a schematic cross-sectional view of a CMP apparatushaving a fifth embodiment of a polishing endpoint detecting deviceaccording to the present invention;

[0036]FIG. 11 is a schematic cross-sectional view of another CMPapparatus comprising the first embodiment of the polishing endpointdetecting device according to the present invention;

[0037]FIG. 12 is an enlarged plan view showing the CMP apparatus shownin FIG. 11;

[0038]FIG. 13 is a schematic cross-sectional view of another CMPapparatus comprising the second embodiment of the polishing endpointdetecting device according to the present invention; and

[0039]FIG. 14 is a schematic cross-sectional view of another CMPapparatus comprising the third embodiment of the polishing endpointdetecting device according to of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] The present invention will be described in detail hereinafter,with reference to the attached drawings.

[0041] FIGS. 3-6 illustrate a first embodiment of a CMP apparatus 200according to the present invention. Referring first to FIG. 3, apolishing head 220 holds a semiconductor substrate 10 so that a surface10 a of the semiconductor substrate 10 to be polished faces a polishingpad 202. The polishing head 220 also urges the semiconductor substrate10 into contact with a polishing pad 202 during the polishing of thesemiconductor substrate 10. More specifically, the polishing head 220exerts suction on the backside of the semiconductor substrate 10 andmoves up and down. In addition, the polishing head 220 rotates in astate in which the semiconductor substrate 10 contacts the polishing pad202 in order to effect a uniform polishing of the semiconductorsubstrate 10. In this case, the polishing pad 202 is made of alight-transmitting (transparent) material such as polyurethane. In thefigure, reference numeral 224 designates a slurry supplying member thatdispenses slurry 224 a onto the polishing pad 202 and hence, between thepad 202 and the substrate 10. Reference numeral 222 designates apolishing pad surface conditioner.

[0042] A rotary plate 212 in the shape of a disc is made of atransparent material and in particular, a plastic such as an acrylicacid resin. The polishing pad 202 is adhered to an upper surface of therotary plate 212. The rotary plate 212 is coupled to a rotary shaft 226that rotates the rotary plate 212.

[0043] A polishing endpoint detecting device 230 for detecting thepolishing endpoint is installed under the rotary plate 212. Thepolishing endpoint detecting device 230 includes a light source 234 forgenerating a beam of light 232 a, such as an infrared laser beam, alight path changing unit 240 for changing the path of the light 232 aemanating from the light source 234, a light measuring instrument 236for measuring a characteristic of the light 232 c reflected from thesurface 10 a of the semiconductor substrate 10 being polished, and aprocessor 250 for detecting the polishing endpoint by analyzing signalsproduced by the light measuring instrument 236.

[0044] The light path changing unit 240 includes a splitter 242, and amotor 244 for rotating the splitter 242 so that the light 232 b scansthe surface 10 a of the semiconductor substrate 10 being polished. Tothis end, the splitter 242 and the motor 244 are coupled to each otherby means of a timing belt 246 and a pair of driving pulleys 248 a and248 b. In this embodiment, the motor 244 is a step motor by which therotational angle of the output shaft thereof can be preciselycontrolled. A controller 252 connected to the motor 244 controls theangular velocity and angle of rotation of the motor 244.

[0045] Referring now to FIGS. 3, 4 and 5, the splitter 242 is rotated bythe motor 244 to change the path of the light 232 b emanating from thelight source 234 such that the light scans the surface 10 a of thesemiconductor substrate 10 along a horizontal line 260 which passesthrough the center of the polishing pad 202. In FIGS. 4 and 5, arrowsrepresent the direction along which the incident light 232 b scans thesurface 10 a of the semiconductor substrate 10. In this case, thehorizontal line 260 also passes through the center of the semiconductorsubstrate 10. The movement of the point of the incident light 232 balong the surface 10 a of the semiconductor substrate 10, and therotation of semiconductor substrate 10 by the polishing head 220 thusallow the entire surface 10 a of the semiconductor substrate 10 to beanalyzed.

[0046] As best shown in FIG. 5, the optical receptor of the lightmeasuring instrument 236 has a surface area that is larger than the area(in the same plane) onto which the light 232 c can be reflected from thesurface 10 a of the semiconductor substrate 10, given the entire rangeof incident angles possible with the splitter 242. In the firstembodiment of the present invention, the light measuring instrument 236can be movable in this plane along with the point of the scanned andreflected light 232 c even though the effective surface area of thelight measuring instrument 236 is large enough to receive the light 232c when the instrument is still.

[0047] In the meantime, the light source 234 and the light measuringinstrument 236 are connected to the processor 250 that controls thegeneration of the light and analyzes the signals output by the lightmeasuring instrument 236 to detect the polishing endpoint. In this case,the processor 250 can detect the polishing endpoint by analyzing theintensity (flux) of the light 232 c reflected from the surface 10 a ofthe semiconductor substrate 10. For example, the CMP process may be usedto planarize an insulation film formed over a metal film on thesemiconductor substrate 10. In this case, when the metal film is exposedduring the polishing of the insulation film, the intensity of thereflected light 232 c measured by the light measuring instrument 236abruptly changes because the reflection ratio of the metal film (ratioof reflected light to absorbed light) is different from that of theinsulation film. The processor 250 perceives the time at which theintensity of the reflected light 232 c abruptly changes as the polishingendpoint of the chemical-mechanical polishing process. On the otherhand, the processor 250 can detect the polishing endpoint from theinterference pattern of the reflected light 232 c. In this case, thereflected light 232 c includes (first) light reflected from theinsulation film and (second) light reflected from the metal film. Theprocessor 250 detects the polishing endpoint based on the phasedifference between the first reflected light and the second reflectedlight.

[0048] Furthermore, the processor 250 determines the amount of polishingthat has been carried out on respective portions of the semiconductorsubstrate 10 by correlating the signals provided by the light measuringinstrument 236 with information concerning the angular velocity andrelative rotational position of the splitter 242. A display 254connected to the processor 250 shows these results of the analysis ofthe signals provided by the light measuring instrument 236. Although notshown in FIGS. 3, 4 and 5, the controller 252 not only controls thesplitter 242 but also the angular velocity of the rotary plate 212, theangular velocity of the polishing head 220, and the pressure createdbetween the semiconductor substrate 10 and the polishing pad 202. Inaddition, the controller 252 controls the flow rate of the slurry 224 aissuing from the slurry supplying member 224 and the operation of thepad conditioner 222 for improving the surface condition of the polishingpad 202.

[0049] Furthermore, if the light measuring instrument 236 werepositioned directly under the splitter 242, the light 232 c reflectedfrom the semiconductor substrate 10 would impinge the splitter 242. Toprevent such problems, as shown in FIG. 6, the plane of the reflectingsurface of the splitter 242 subtends a predetermined angle with respectto the horizontal, and the light measuring instrument 236 is spacedlaterally from the splitter 242 by a corresponding amount.

[0050] According to the first embodiment of the present invention, light232 b is directed onto the surface 10 a of the semiconductor substrate10 through the transparent rotary plate 212 and polishing pad 202. Thelight 232 b is also scanned across the surface 10 a of the semiconductorsubstrate 10 by the splitter 242. The light 232 b scanning the surface10 a of the semiconductor substrate 10 is reflected from the surface 10a onto the light measuring instrument 236. Therefore, all portions ofthe surface 10 a of the semiconductor substrate 10 being polished can beanalyzed to prevent them from being over-polished or under-polished.Also, the amount that any portion of the semiconductor substrate 10 hasbeen polished can be determined regardless of the rotational speed ofthe rotary plate 212 and polishing pad 202 because the plate 212 and thepolishing pad 202 are made of light-transmitting materials. Furthermore,the amount of slurry 224 a or by-product that accumulates between thesurface 10 a of the semiconductor substrate 10 and the polishing pad 202is relatively low because there is no gap therebetween corresponding tothe gap that exists between a substrate and the transparent window ofthe conventional polishing pad. Hence, the polishing endpoint detectionprocess is more reliable than in the prior art. Still further, verylittle time is required for changing the polishing pad 202 because therotary plate 212 and the polishing pad 202 are both made entirely oflight-transmitting material, i.e., do not have to be rotationallyaligned relative to one another.

[0051]FIG. 7 is shows a CMP apparatus 300 having another polishingendpoint detecting device 330 according to the present invention. TheCMP apparatus 300 also includes a rotary plate 312 of a transparentmaterial such as an acrylic acid resin, and a polishing pad 302 of alight-transmitting material attached to the rotary plate 312. Thepolishing endpoint detecting device includes a light source 334 and alight measuring instrument 336 disposed under the rotary plate 312. Thelight source 334 directs a beam of light 332 a onto a surface 10 a of asemiconductor substrate 10 being polished. The light 232 a impinges thesurface 10 a at a predetermined incident angle after the light 332 a haspassed through the plate 312 and the polishing pad 302. The lightmeasuring instrument 336 measures a characteristic of the light 332 breflected from the surface 10 a of the semiconductor substrate 10.

[0052] A scanning mechanism 340 supports the light source 334 and thelight measuring instrument 336. The scanning mechanism 340 is alsooperative to scan the incident light 332 a over the surface 10 a of thesemiconductor substrate 10 along a horizontal line passing through thecenter of the polishing pad 302. The scanning mechanism 340 includes asupporting member 342 for supporting the light source 334 and the lightmeasuring instrument 336, and a pneumatic cylinder 344 for reciprocallymoving the supporting member 342 in a straight line. When the pneumaticcylinder 344 moves the supporting member 342, the point where the light332 a from the light source 334 impinges the surface 10 a of thesemiconductor substrate 10 moves along the aforementioned horizontalline passing through the center of the polishing pad 312.

[0053] A processor 350 is connected to the light source 334 and thelight measuring instrument 336, and a controller 352 is connected to thepneumatic cylinder 344. Although a pneumatic cylinder 344 is shown inFIG. 7 as the means for reciprocally moving the supporting member 342,other linear reciprocal driving mechanisms can be employed. Also,although the controller 352 and the pneumatic cylinder 344 are shown asbeing directly connected, the controller 352 can further include adirection control valve for controlling the flow of compressed air toand from the cylinder 344 and a flow rate control valve for controllingthe flow rate of the compressed air. Otherwise, the functions of theprocessor 350, the controller 352 and the display 354 are identical tothose of the first embodiment.

[0054] According to the second embodiment of the present invention, thelight 332 a directed onto the surface 10 a of the semiconductorsubstrate 10 being polished scans the surface 10 a of the semiconductorsubstrate 10 in accordance with the extension and retraction of thepneumatic cylinder 334. The light 332 b reflected from the surface 10 aof the semiconductor substrate 10 is measured by the light measuringinstrument 336. Therefore, all of the polished portions of the surface10 a of the semiconductor substrate 10 can be analyzed. Such an analysiscan be used to prevent the over-polishing or the under-polishing of thesurface 10 a. Also, the amounts by which all of the portions of thesemiconductor substrate 10 have been polished can be measured regardlessof the angular velocity of the rotary plate 312 and the polishing pad302 because the plate 312 and the polishing pad 302 each compriselight-transmitting material.

[0055]FIG. 8 shows a CMP apparatus 400 having a third embodiment of apolishing endpoint detecting device 430 according to the presentinvention. Referring to FIG. 8, a polishing pad 402 of alight-transmitting material (same as first embodiment) is attached to atransparent rotary plate 412. A light source 434, a splitter 436 and alight measuring instrument 438 are disposed under the rotary plate 412.The light source 434 emits a beam of light 432 a, and the splitter 436changes the path of the emitted light 432 a so that the light 432 a isdirected onto the surface 10 a of the semiconductor substrate 10 beingpolished. The light measuring instrument 438 measures a characteristicof the light 432 c reflected from the surface 10 a of the semiconductorsubstrate 10.

[0056] A light path changing device 440 is operative to scan the light432 b from the splitter 436 across the surface 10 a of the semiconductorsubstrate 10 along a horizontal line 260 (see FIG. 4) passing throughthe center of the polishing pad 402. The light path changing device 440includes a supporting member 442 supporting the light source 434, thesplitter 436 and the light measuring instrument 438, and a pneumaticcylinder 444 for reciprocally moving the supporting member 442 in astraight line. The pneumatic cylinder 444 moves the supporting member442 so that the point of light 432 b impinging on the surface 10 a ofthe semiconductor substrate 10 moves along a horizontal line passingthrough the center of the polishing pad 402 and the center of thesemiconductor substrate 10. A processor 450 is connected to the lightsource 434 and the light measuring instrument 438, and a controller 452is connected to the pneumatic cylinder 444.

[0057] Although a pneumatic cylinder 444 is shown in FIG. 8 as the meansfor reciprocally moving the supporting member 442, other linearreciprocal driving mechanisms can be employed. Also, although thecontroller 452 and the pneumatic cylinder 444 are shown as beingdirectly connected, the controller 452 can further include a directioncontrol valve for controlling the flow of compressed air to and from thecylinder 444 and a flow rate control valve for controlling the flow rateof the compressed air. The processor 450 detects a polishing endpoint byanalyzing the signals produced by the light measuring instrument 438,and the controller 452 controls the operation of the pneumatic cylinder444. Otherwise, the functions of the processor 450, the controller 452and a display 454 are identical to those of the first embodiment.

[0058]FIG. 9 shows a CMP apparatus 500 having a fourth embodiment of apolishing endpoint detecting device 530 according to the presentinvention. Referring to FIG. 9, a polishing pad 502 of alight-transmitting material is attached to a transparent rotary plate512. A light source 534, a splitter 536 and a light measuring instrument538 are disposed under the rotary plate 512 and polishing pad 502. Thelight source 534 emits a beam of light 532 a. The light 532 a from thelight source 534 passes through the rotary plate 512 and the polishingpad 502 and impinges on the surface 10 a of the semiconductor substrate10 at a predetermined angle of incidence. The light 532 b reflectingfrom the surface 10 a impinges on the splitter 536, whereby the light532 b reflected from the surface 10 a of the semiconductor substrate 10being polished is directed onto the light measuring instrument 538. Thelight measuring instrument 538 measures a characteristic of the light532 c reflecting from the splitter 536.

[0059] The polishing endpoint detecting device 530 also comprises alight path changing device 540 including a supporting member 542supporting the light source 534, the splitter 536, and the lightmeasuring instrument 538, and a pneumatic cylinder 544 connected to thesupporting member 542. Also, the polishing endpoint detecting device 530includes a processor 550 for detecting a polishing endpoint by analyzingthe signals produced by the light measuring instrument 538, a controller552 for controlling the operation of the pneumatic cylinder 544, and adisplay 554. The light path changing device 540, the processor 550, thecontroller 552 and the display 554 are similar to those of the thirdembodiment of FIG. 8 and as such, a detailed description thereof will beomitted.

[0060]FIG. 10 illustrates a CMP apparatus 600 having a fifth embodimentof a polishing endpoint detecting device 630 according to the presentinvention. Referring to FIG. 10, a polishing pad 602 of alight-transmitting material is attached to a transparent rotary plate612. A light source 634, a splitter 636 (of a half-mirror type) and alight measuring instrument 638 are disposed under the plate 612 andpolishing pad 602.

[0061] The splitter 636 is positioned over the light source 634 asoriented with a predetermined angle of inclination. The light source 634emits a beam of light 632 a vertically towards the surface 10 a of thesemiconductor substrate 10 being polished. The splitter 636 transmits aportion of 632 b of the light 632 a from the light source 634, andreflects the remainder 632 c of the light 632 a. The light 632 b passingthrough the splitter 636 impinges on the surface 10 a of thesemiconductor substrate 10. A portion 632 e of the light 632 d reflectedfrom the surface 10 a of the semiconductor substrate 10 is reflected bythe splitter 636, and the rest 632 f of the light 632 d passes throughthe splitter 636. A characteristic of the light 632 e reflected from thesurface 10 a of the semiconductor substrate 10 and reflected by thesplitter 636 is measured by the light measuring instrument 638.

[0062] The polishing endpoint detecting device 630 also comprises alight path changing device 640 including a supporting member 642supporting the light source 634, the splitter 636, and the lightmeasuring instrument 638, and a pneumatic cylinder 644 connected to thesupporting member 642. Also, the polishing endpoint detecting device 630includes a processor 650 for detecting a polishing endpoint by analyzingthe signals produced by the light measuring instrument 638, a controller652 for controlling the operation of the pneumatic cylinder 644, and adisplay 654. The light path changing device 640, the processor 650, thecontroller 652 and the display 654 are similar to those of the thirdembodiment of FIG. 8 and as such, a detailed description thereof will beomitted.

[0063]FIG. 11 illustrates another embodiment of a CMP apparatus 700having a polishing endpoint detecting device 730 corresponding to thatof the first embodiment. Referring FIG. 11, the CMP apparatus 700includes a rotational table 710 to which a polishing pad 702 of alight-transmitting material is attached. The polishing endpointdetecting device 730 is disposed within the rotational table 710. Apolishing head 720 holds the semiconductor substrate 10 opposite thepolishing pad 702 and presses the surface 10 a of the semiconductorsubstrate 10 into contact with the polishing pad 702 during thepolishing process. The CMP apparatus also includes a pad conditioner 722for improving the surface condition of the polishing pad 702, and aslurry supplying member 724 for supplying slurry 724 a onto thepolishing pad 702.

[0064] The rotational table 710 includes a rotary plate 712 of alight-transmitting material to which the polishing pad 702 is attached,a base plate 716 spaced a predetermined distance from the rotary plate712 and coupled to a rotary shaft 726 that provides the rotational driveforce for the rotational table 710, and a sidewall 714 extending alongand between the outer peripheral edges of the base plate 716 and therotary plate 712. The rotational table 710 thus has the overall shape ofa disc, and defines an inner space 718 delimited by the rotary plate712, the sidewall 714, and the base plate 716.

[0065] The polishing endpoint detecting device 730 is disposed in theinner space 718 of the rotary table 710 as mounted on the base plate716. The polishing endpoint detecting device 730 includes a light source734 for producing a beam of light, a splitter 742 for changing the pathof the light so that the light emanating from the light source 734 isdirected onto the surface 10 a of the semiconductor substrate 10, alight measuring instrument 736 for measuring a characteristic of thelight reflected from the surface 10 a of the semiconductor substrate 10,and a motor 744 for rotating the splitter 742 so that the light appliedto the surface 10 a of the semiconductor substrate 10 by the splitter742 scans the surface 10 a along a horizontal line 760 (see FIG. 12)that passes through the center of the polishing pad 702.

[0066] A processor 750 and a controller 752 are disposed outside therotary table 720. The processor 750 detects a polishing endpoint byanalyzing the signals produced by the light measuring instrument 736,and the controller 752 controls the angular velocity and relativerotational position of the output shaft of the motor 744. The processor750 and the controller 752 are connected to the light source 734, thelight measuring instrument 736 and the motor 744 through rotary shaft726. A display 754 is connected to the processor 750. In addition,although not shown, a linear reciprocal drive mechanism and supportingmember can be disposed on the base plate 716 in order to move the lightmeasuring instrument along a straight line.

[0067] In addition, a light sensor 756 having a light emitting portionand a light receiving portion cooperates with a peripheral portion ofthe rotational table 710 in order to effect a sampling of the signalsproduced by the light measuring instrument 736 which rotates togetherwith the rotational table 710. The peripheral portion of the rotationaltable 710 with which the light sensor 756 cooperates is disposedopposite the polishing endpoint detecting device 730 with respect to thecenter of rotation of table 710. The light sensor 756 is connected tothe controller 752 coupled to the processor 750. When the peripheralportion of the table 710 blocks the transmission of light from the lightemitting portion to the light receiving portion of the light sensor 756,the processor 750 samples the signals produced by the light measuringinstrument 736.

[0068] As shown in FIG. 12, the light applied to the surface 10 of thesemiconductor substrate 10 scans the surface 10 a of the semiconductorsubstrate 10 along a horizontal line 760 passing through the centers ofthe polishing pad 702 and the semiconductor substrate 10. At that time,the point 10 c on the surface 10 a of the semiconductor substrate 10,impinged by the light coming from the splitter 742 moves by regularintervals along the horizontal line 760. Such interval is determined bythe rotational speed of the motor 744, and is related to the rotationalspeed of the rotational table 710. The rotational speeds of the motor744 and the table 710 can be set according to the parameters of thepolishing process.

[0069] The amount by which the semiconductor substrate 10 is polished isthus measured with respect to the entire surface 10 a of thesemiconductor substrate 10, and the processor 750 detects the polishingendpoint based on this amount. Therefore, the over-polishing orunder-polishing of the semiconductor substrate 10 can be prevented.Also, because the rotary plate 712 and the polishing pad 702 eachcomprise light-transmitting material, very little time is required forchanging the polishing pad 702.

[0070]FIG. 13 illustrates a CMP apparatus 800 having a polishingendpoint detecting device 830 corresponding to the second embodiment ofthe present invention. Referring FIG. 13, the CMP apparatus 800 includesa rotational table 810 to which a polishing pad 802 of alight-transmitting material is attached, a polishing endpoint detectingdevice 830 installed in the rotational table 810, a polishing head 820for holding a semiconductor substrate 10 to be polished so that asurface 10 a of the semiconductor substrate 10 faces and is pressed intocontact with the polishing pad 802, a pad conditioner 822 for improvinga surface condition of the polishing pad 802, and a slurry supplyingmember 824 for supplying slurry 824 a onto the polishing pad 802.

[0071] The rotational table 810 has a rotary plate 812 of alight-transmitting material to which the polishing pad 802 is attached,a base plate 816 coupled to a rotary drive shaft 826, and a sidewall 814extending along and between the outer peripheral edges of the base plate816 and the rotary plate 812. The polishing table 810 thus has theoverall shape of a disc, and an inner space 818 delimited by the rotaryplate 812, the sidewall 814 and the base plate 816.

[0072] The polishing endpoint detecting device 830 is installed in theinner space 818 of the rotational table 810 as supported by the baseplate 816. The polishing endpoint detecting device 830 includes a lightsource 834 for producing a beam of light, a light measuring instrument836 for measuring a characteristic of the light reflected from thesurface 10 a of the semiconductor substrate 10, a supporting member 842for supporting the light source 834 and the light measuring instrument836, and a pneumatic cylinder 844 coupled to the supporting member 842.The pneumatic cylinder 844 reciprocally moves the supporting member 842in a straight line so that the light emanating from the light source 834scans the surface 10 a of the semiconductor substrate 10 along ahorizontal line which passes through the center of the polishing pad802.

[0073] A processor 850 for detecting a polishing endpoint by analyzingthe signals from the light measuring instrument 836, and a controller852 for controlling the operation of the pneumatic cylinder 844, aredisposed outside the rotational table 810. The processor 850 and thecontroller 852 are connected to the light source 834, the lightmeasuring instrument 836 and the pneumatic cylinder 844 through therotary shaft 826. In addition, though not shown, a guide can be disposedon the base plate 816 to guide the supporting member 842 for movementalong a straight line.

[0074] A light sensor 856 cooperates with a peripheral portion of therotational table 810 to effect the sampling of the signals produced bythe light measuring instrument 836, and a display 854 showing theresults of the analysis of these signals is connected to the processor850. Further detailed descriptions of these elements will be omittedbecause these elements are similar to those already described inconnection with the polishing endpoint detection device 330 shown inFIG. 7 and the CMP apparatus 700 shown in FIGS. 11 and 12.

[0075]FIG. 14 illustrates a CMP apparatus 900 having a polishingendpoint detecting device 930 corresponding to that of the thirdembodiment of the present invention. Referring FIG. 14, the CMPapparatus 900 has a rotational table 910 to which a polishing pad 902 ofa light-transmitting material is attached, a polishing endpointdetecting device 930 installed in the rotational table 910, a polishinghead 920 holding a semiconductor substrate 10 to be polished so that asurface 10 a of the semiconductor substrate 10 is disposed opposite andis pressed into contact with the polishing pad 902 during a polishingprocess, a pad conditioner 922 for improving a surface condition of thepolishing pad 902, and a slurry supplying member 924 for supplying aslurry 924 a onto the polishing pad 902.

[0076] The rotational table 910 includes a rotary plate 912 of alight-transmitting material to which the polishing pad 902 is attached,a base plate 916 coupled to a rotary shaft 926, and a sidewall 914extending along and between the outer peripheral edges of the base plate916 and the rotary plate 912. The rotational table 910 thus has theoverall shape of a disc, and an inner space 918 delimited by the rotaryplate 912, the sidewall 914 and the base plate 916.

[0077] The polishing endpoint detecting device 930 is installed in theinner space 918 of the rotational table 910 as supported by the baseplate 916. The polishing endpoint detecting device 930 includes a lightsource 934 for producing a beam of light, a splitter 936 for changingthe path of the light so that the light emanating from the light source934 is directed onto the surface 10 a of the semiconductor substrate 10,a light measuring instrument 938 for measuring a characteristic of thelight reflected from the surface 10 a of the semiconductor substrate 10,a supporting member 942 supporting the light source 934, the splitter936, and the light measuring instrument 938, and a pneumatic cylinder944 coupled to the supporting member 942. The pneumatic cylinder 944moves the supporting member 942 reciprocally in a straight line so thatthe light scans the surface 10 a of the semiconductor substrate 10 alonga horizontal line that passes through the center of the polishing pad902.

[0078] A processor 950 and a controller 952 are disposed outside therotational table 910. The processor 950 detects a polishing endpoint byanalyzing the signals produced by the light measuring instrument 938,and the controller 952 controls the operation of the pneumatic cylinder944. The processor 950 and the controller 952 are connected to the lightsource 934, the light measuring instrument 938 and the pneumaticcylinder 944 through the rotary shaft 926. In addition, although notshown, a guide can be disposed on the base plate 916 to guide thesupporting member 942 for movement along a straight line.

[0079] A light sensor 956 cooperates with a peripheral portion of therotational table 910 to effect a sampling of the signals produced by thelight measuring instrument 938, and a display 954 showing the result ofthe analysis of these signals is connected to the processor 950. Afurther detailed description of these elements will be omitted becausethese elements are similar to those of the polishing endpoint detectingdevice 430 shown in FIG. 8 and the CMP apparatus 700 shown in FIG. 11and FIG. 12.

[0080] According to the present invention, light from a light source isapplied onto a surface of a semiconductor substrate through a rotaryplate to which a transparent polishing pad is attached. The lightapplied onto the surface of the semiconductor substrate is scannedacross the surface of the semiconductor substrate along a horizontalline passing through the centers of the polishing pad and thesemiconductor substrate. A light measuring instrument measures acharacteristic of the light reflected from the surface of thesemiconductor substrate. A processor detects a polishing endpoint byanalyzing signals produced by the light measuring instrument asrepresentative of a characteristic of the light reflected from thesurface of the semiconductor substrate.

[0081] Therefore, the amount that the entire surface of thesemiconductor substrate has been polished can be measured, whereby thepolishing endpoint detected can prevent the over-polishing orunder-polishing of the semiconductor substrate. Also, little slurry orby-product of the polishing process accumulates between the surface ofthe semiconductor substrate and the polishing pad. Accordingly, thepolishing endpoint is detected with a high degree of reliability.

[0082] Furthermore, because the polishing pad and the rotary plate areof light-transmitting materials, they do not have to be aligned in acircumferential direction. Therefore, very little time is required forchanging the polishing pad, whereby the downtime of the CMP apparatus iskept to a minimum and the productivity of the CMP process is enhanced.

[0083] Finally, although the present invention has been described abovewith reference to the preferred embodiments thereof, it is evident thatmany modifications and variations thereof will be apparent to thosehaving ordinary skill in the art. Accordingly, all such modificationsand variations are seen to be within the true spirit and scope of theinvention as defined by appended claims.

What is claimed is:
 1. A polishing endpoint detecting device for use indetecting a polishing endpoint of a process of polishing a surface of asubstrate, comprising: a light source for producing a beam of light tobe provided onto a surface of the substrate being polished by apolishing pad that is transparent with respect to the beam of light;light path changing means for changing a path of the beam of light sothat the beam of light scans the surface of the substrate along ahorizontal line across the surface of the substrate; a light measuringinstrument operative to produce signals representative of acharacteristic of a light reflected from the surface of the substrateand to output the signals; and a processor connected to the lightmeasuring instrument so as to receive the signals produced by the lightmeasuring instrument and configured to analyze the signals to detect apolishing endpoint of the polishing process.
 2. The polishing endpointdetecting device of claim 1, wherein the horizontal line passes througha center of the polishing pad.
 3. The polishing endpoint detectingdevice of claim 1, wherein the light path changing means comprises areflective splitter, and driving means for rotating the splitter.
 4. Thepolishing endpoint detecting device of claim 1, wherein the light pathchanging means comprises a supporting member supporting the light sourceand the light measuring instrument, and driving means for moving thesupporting member reciprocally along a straight line.
 5. The polishingendpoint detecting device of claim 4, wherein the light path changingmeans further comprises a reflective splitter oriented to direct thebeam of light produced by the light source onto the surface of thesubstrate.
 6. The polishing endpoint detecting device of claim 4,wherein the light path changing means further comprises a reflectivesplitter oriented to direct the light reflected from the scanned surfaceof the substrate to the light measuring instrument.
 7. The polishingendpoint detecting device of claim 6, wherein the splitter is partiallytransmitting with respect to the beam of light produced by the lightsource, and is disposed above the light source so that some of the lightproduced by the light source directs onto the surface of the substratethrough the splitter.
 8. A chemical-mechanical polishing apparatuscomprising: a light source that produces a beam of light; a rotationaltable rotatable about a central axis of rotation, the rotational tableincluding a rotary plate including a first material that is transparentwith respect to the light produced by the light source, and a polishingpad including a second material that is transparent with respect to thelight produced by the light source, the polishing pad being attached tothe rotary plate; a polishing head disposed above the polishing pad forholding a substrate such that a surface of the substrate faces thepolishing pad and is pressed into contact with the polishing pad, androtating the substrate while the surface of the substrate is in contactwith the polishing pad; light path changing means for changing a path ofthe beam of light so that the beam of light scans the surface of thesubstrate along a horizontal line across the surface of the substrateheld against the polishing pad by the polishing head through the rotaryplate and the polishing pad; a light measuring instrument operative toproduce signals representative of a characteristic of a light reflectedfrom the surface of the substrate; and a processor connected to thelight measuring instrument so as to receive the signals produced by thelight measuring instrument and configured to analyze the signals todetect a polishing endpoint of the polishing process.
 9. Thechemical-mechanical polishing apparatus of claim 8, wherein therotational table further includes a rotary shaft having a centrallongitudinal axis corresponding to the axis of rotation, a base platemounted to the rotary shaft, and a sidewall extending between and alongouter peripheral edges of the rotary plate and the base plate, whereinthe rotational table has an inner space delimited by the base plate, thesidewall and the rotary plate, and wherein the light source, the lightpath changing means and the light measuring instrument are disposed inthe inner space as supported by the base plate.
 10. The polishingendpoint detecting device of claim 9, wherein the light path changingmeans comprises a reflective splitter, and driving means for rotatingthe splitter.
 11. The polishing endpoint detecting device of claim 8,wherein the light path changing means comprises a reflective splitter,and driving means for rotating the splitter.
 12. The polishing endpointdetecting device of claim 8, wherein the light path changing meanscomprises a supporting member supporting the light source and the lightmeasuring instrument, and driving means for moving the supporting memberreciprocally along a straight line.
 13. The polishing endpoint detectingdevice of claim 12, wherein the light path changing means furthercomprises a reflective splitter that reflects the beam of light.
 14. Thepolishing endpoint detecting device of claim 12, wherein the splitter ispartially transmitting with respect to the beam of light produced by thelight source, and is disposed above the light source so that some of thelight produced by the light source directs onto the surface of thesubstrate through the splitter.
 15. The polishing endpoint detectingdevice of claim 9, wherein the light path changing means comprises asupporting member supporting the light source and the light measuringinstrument, and driving means for moving the supporting memberreciprocally along a straight line.
 16. The polishing endpoint detectingdevice of claim 8, wherein the horizontal line passes through a centerof the polishing pad.
 17. The chemical-mechanical polishing apparatus ofclaim 8, wherein the first material includes an acrylic acid resin. 18.The chemical-mechanical polishing apparatus of claim 8, wherein thesecond material includes polyurethane.
 19. The chemical-mechanicalpolishing apparatus of claim 8, further comprising a display for showingan analysis result of the processor.
 20. The chemical-mechanicalpolishing apparatus of claim 8, further comprising a slurry supplymember disposed above the polishing pad for supplying a slurry onto thepolishing pad.